You and your stuff live below the door and window frames, so decorate there. If that is done right, no one will notice the big walls above, except you (especially when the heat and air bills come in!) A credenza 25% wider than the TV will take care of that issue for you. Since you may be having issues with echo in such a hard volume, continue adding fabric to dampen the sound. Stationary drapery panels hung at ceiling level where the vault joins the wall will do a lot for the space in many ways. I suggest you need to add some pattern at the windows for interest. Is the empty space to be for dining or something else?

The empty space is the foyer.

Have you ever thought of mounting the TV above the fireplace? Move the couches closer to the fireplace, and do a little sitting/reading area where the console/TV is now. On the opposite side (foyer), have a long table against the wall with a mirror above it, lamps on each side, and a rug runner so it's your entryway's welcoming area. I don't know the dimensions of the rooms but you could try it to see how it all fits. Then add the drapery panels like and more texture with baskets, pillows, throws, etc.

Sally, I have considered putting the TV above the fireplace. I have two reservations. One is the fireplace is high so it may be uncomfortable to watch the TV above it. The other is that it is one of the first things you see as soon as you walk into the front door. Though, if the foyer and living room are decorated nicely, I suppose it wouldn't be a big deal. Thanks for your suggestions!

http://www.digitaltrends.com/home-theater/please-dont-mount-your-tv-over-the-fireplace/